time signatures and measure grouping

[Tapio Tuovila]

Hi all,
some questions: -using lilypond-2.4.4 on SuSE-9.2

1) for teaching purposes I'd like measure groupings in the output as 
shown in site 5.3.5 Time signature. I've got a piece in 7/8 with 
groupings 2+2+3 and 3+2+2. I can print the groupings using

#(set-time-signature 7 8 '( 2 2 3))
and
#(set-time-signature 7 8 '( 3 2 2))

but when the grouping changes the output prints also the time signature 
which does not change.

Is there a way to avoid the unnecessary time signatures?

2) Can these groupings be shown upon a RhythmicStaff? How?

3) How can I change the line-count of a staff;  I'd like to have staves 
also with 1 and 2 lines? -A small example would be most welcome, as I 
have not been able to figure out how this should be done in the 
documentation and the user-archives search is not working.

my best,
Tapio